Computing at the speed of light

For Sergio Cantu, a second-year PhD student in physics, the future of computing is one in which information moves at the speed of light, and through a network with unparalleled security.

Sergio CantuPhoto: Bryce Vickmark

In Cantu’s eyes, much of this future is predicated on lasers — which he’s worked with not only as a graduate student, but as an undergraduate at the University of Texas at Brownsville and in the year after graduating, as a student in MIT’s Physics Bridge Program, which aims to facilitate students’ transition to PhD coursework. It was during the latter experience that he first set foot in MIT’s Center for Ultracold Atoms, where he conducts research today.

“Lately, atomic physics has been going through a renaissance, and for me it was very exciting to join that effort,” Cantu says. “We can control a laser frequency at a much higher precision and accuracy now. This allows us to have better control over how we use them to interact with atoms.”

Quantum computing

Cantu’s research uses light as an information carrier in computing and calculating. Because of light’s unmatched speed, it could support extremely fast and efficient computing, well beyond our current capabilities. But, he cautions, light comes with challenges — many of which are caused by its very speed.

“It doesn’t slow down, it’s always moving, and that makes it very hard to use as a carrier of information,” Cantu says. “How do you imprint information on something that you can’t pin down?”

One of the techniques that Cantu and his colleagues use is called electromagnetically induced transparency. This technique allows scientists to slow the speed of propagation of light, while it travels through an atomic gas, to about 100 meters per second, more than a million times slower than the speed of light in a vacuum. This allows him to manipulate matter — clusters of atoms — one unit of light at a time. Light doesn’t like to interact with much — sometimes not even with itself — but Cantu and his team can map specific interactions between light and atoms, at the level of individual photons, and use that as a way to transmit and exchange information.

“The light we’re working with comes in the form of lasers with different wavelengths — a red laser versus a green laser, for example,” Cantu says. “[Each wavelength of] light interacts differently with matter, and can be used to transmit a diversity of information.”

Ultra security

Right now, computers send information back and forth through optical fibers. But by this method, a third party can potentially intercept a message without its receiver knowing that the line isn’t secure. What excites Cantu most about quantum computing is that computing at the level of photons prohibits this type of sneaky interception.

If a third party got hold of information being sent through particles of light, the message’s intended recipient would receive an incomplete message, and instantly be able to tell that someone was trying to gain unauthorized access.

Quantum computing is almost like sending a message very quickly, but one letter at a time. In attempting to intercept a message, a third party would only get hold of a handful of letters, and the message on the receiver’s end would be missing those exact letters, making it obvious that someone was trying to interfere. This level of security could be most useful for governments and financial institutions, but it could also find uses in personal computers.

“I usually only send people pictures of cats, but they’re very secure pictures of cats,” Cantu jokes. “But the point of quantum computing is that it will allow you to interact with the world much more securely, and for me that’s a huge advantage no matter who you are or what you’re sending.”

A rocky beginning

Although Cantu is on solid footing now, he had a rough start at MIT: He took a midterm, feeling well prepared, but received a score of only 9 out of 100.

“For me, that was a huge reality check,” Cantu says. “I didn’t understand why I was struggling with the class.”

Then he realized it was his attitude. The week after the exam, he noticed an older man in the class who was very attentive. When the professor offered the class a chance to retake the midterm, he decided to emulate his motivated classmate. He got a score of 99 the second time around, and walked away with a different mindset.

“That was when I learned that sometimes you have to be brought all the way down to find your way back up to the top,” he recalls. “I don’t assume that I should know the answers anymore, and I’ve become a lot more active in how I ask questions or approach problems. My research experience has been so much more positive since then.”

Cantu also attributes some of his rocky beginning at MIT to his upbringing. Growing up along the Texas-Mexico border, he recalls not having much early exposure to science. He’s since become part of a network of students with similar backgrounds in a nonprofit called Clubes de Cienca, which sends scientists to Mexico to help bridge this gap. The group has already reached over 1,000 students, sending 75 scientists to six cities throughout the country. Cantu is primarily involved with securing funding for the organization, and coordinating logistics once the scientists arrive in Mexico.

“Not a lot of people in my community go into science, unfortunately, and I think it’s because the way science is taught, it loses its humanity,” Cantu says. “Science, at the end of the day, is done by people just like you and me, and to me that was always very striking, so I want to give others that view, too.”